Sebastian Stan, who has played the Mad Hatter since 2012, will not be reprising his role later this season when the character returns, and the network has begun looking for a replacement. ABC and the producers hoped that Stan could have continued, but he was unavailable for long-term work. (On the docket for Stan is the Captain America: The Winter Soldier.)

Though the spinoff project is in the very early stages, ABC is mulling whether a short presentation will be filmed or a backdoor pilot will air later this season. It would be a late addition to ABC's pilot pool and would be vying for a fall 2013 slot.

Once Upon a Time executive producers Adam Horowitz and Eddy Kitsis are overseeing the spinoff idea and would serve as showrunners on both series should the Mad Hatter project go.

This is a big move on ABC's part to expand the Once Upon a Time franchise at a time when networks are banking on established franchises to kick-start new series. The CW's The Originals backdoorpilot, a spinoff of The Vampire Diaries, will air in April,and CBS continues its tried-and-true practice with an NCIS: LA spinoff Red airing later in the season.

Once Upon a Time has proven to be a consistent performer opening ABC's Sunday night block. ABC hasyet to have a huge breakout hit this season, with Once Upon a Time lead-out Revenge skidding and freshman dramas Last Resort and 666 Park Avenue getting the ax.